Two-stage smokeless incinerator with fluidized bed first stage

ABSTRACT

Waste products are uncinerated in a two-stage incinerator wherein in the first stage the waste products to be incinerated are at least partially fluidized. Hot gases exiting the second stage are quenched with ambient air which reduces stack insulation requirements. The quenched gases can be used to provide preheated air for the first or second stage combustion air, and can be used as the fluidizing gas stream in the first stage. The two-stage incinerator and process provides effective oxidative incineration, with gaseous products being smokeless, and any non-vaporized non-combusted solid matter essentially retained in the first stage.

Pryor et al.

1 Nov. 19, 1974 TWO-STAGE SMOKELESS INCINERATOR WITH FLUIDIZED BED FIRSTSTAGE lnventors: Robert C. Pryor; Howard M. Katz,

both of Bartlesville, Okla.

Phillips Petroleum Company, Bartlesville, Okla.

Filed: May- 11, 1973 Appl. No.: 359,444

Assignee:

US. Cl. 110/8 A, 110/8 C, 110/28] Int. Cl. F23g 5/12 Field of Search110/8 R, 8 A, 8 C, 18 R,

References Cited UNITED STATES PATENTS lshigaki l 10/ l 5 3,645,218Davis 110/8 Primary Examiner-Kenneth W. Sprague [5 7 ABSTRACT Wasteproducts are incinerated in a two-stage incinerator wherein in the firststage the waste products to be incinerated are at least partiallyfluidized. l-lot gases exiting the second stage are quenched withambient air which reduces stack insulation requirements. The quenchedgases can be used to provide preheated air for the first or second stagecombustion air, and can be used as the fluidizing gas stream in thefirst stage. The two-stage incinerator and process provides effec tiveoxidative incineration, with gaseous products being smokeless, and anynon-vaporized noncombusted solid matter essentially retained in the firstage.

20 Claims, 1 Drawing Figure lllllllllllil FFFFSIFFF TWO-STATE SMOKELESSINCINERATOR WITH FLUIDIZED BED FIRST STAGE FIELD OF THE INVENTION Theinvention relates to the incineration of waste products. In anotheraspect, the invention pertains to an incinerator.

BACKGROUND OF THE INVENTION Limited availability of land fills anddumping sites has meant increasing needs for improved methods ofincineration of a wide variety of waste andundesirable materials.Particularly needed are methods of incineration as well as incineratorssuch that any solid noncombustible matter is essentially retained in theincinerator, and at the same time essentially all volatile matter is ascompletely oxidized as possible and produced in gaseous evolution insmokeless form.

OBJECTS OF THE INVENTION It is an object ofour invention to provide aneffective method and apparatus for the incineration of a variety ofwaste products.

Other aspects, objects, and the several advantages of our invention willbe apparent to one skilled in the art from the following disclosure andour appended claims.

SUMMARY OF THE INVENTION According to our invention, waste products areincinerated in a two-stage incinerator in the first stage of which thewaste materials are at least partially fluidized. In one embodiment, thefirst stage comprises a first burner means, a forced air supply means,and a perforated support means arranged to permit fluidizing gases toflow upwardly there through to fluidize and thus burn more efficientlywaste material; and the second stage comprises burner means and forcedair supply. Hot gases exiting the second stage chamber can be quenchedwith ambient air, which reduces stack insulation requirements, and aportion of the quenched gases can be utilized to provide preheated airfor the first and/or second stage combustion air supplies, and/or foruse as the low pressure fluidizing gas stream for the first stage.

The incinerator and method provide effective oxidative incineration,with gaseous products being essentially smokeless, and any non-vaporizednoncombusted solid matter essentially retained in the first stage. Theincinerator and the method of incineration that we have invented anddeveloped are particularly effective in combusting difficultycombustible materials including chunk materials, high ash-contentmaterials, as well as organic wastes of liquid, semisolid, or solidform.

BRIEF DESCRIPTION OF THE DRAWING Our invention can be further visualizedby reference to the accompanying schematic drawing.

The FIGURE shows in elevation form one embodiment of our two-stageincinerator, including a first stage vaporization stage with fluidizedwaste bed, and second stage oxidative combustion stage with ambient airquench zone at the outlet thereof, followed by stack or similar exitmeans for the quenched smokeless effluent, and cycle of quenchedpreheated gases to the first stage as the fluidizing gas stream tofluidize waste products.

DETAILED DESCRIPTION OF THE INVENTION Our incinerator and method ofincinerator comprise a first combustion or vaporization zone in whichwaste material to be combusted or vaporized, supported by means such asa grate, preferably a traveling grate, is fluidized by a stream offluidizing gases flowing upwardly through the support means, and asecond stage or zone wherein final oxidative combustion occurs. In thefirst stage, vaporization or volatilization is achieved by a firstheating means such as a first burner means, preferably in conjunctionwith forced air supply, preferably directing a flame preferably in agenerally downwardly directed manner toward the materials to becombusted. Volatilizable matter is volatilized, and to some extent,generally appreciable, combustion occurs in this first stage, and allgaseous products therefrom are conducted through a closed conduit into acontiguous second stage in which further oxidation and combustion occurthrough the use of a second burner and further supply of forced air. 1

The use of the fluidized bed means in the first stage provides severalbenefits. The preheated underfire fluidizing gases supply combustion airin an amount sufficient to provide at least partial but efficientfluidization of the waste bed, as well as assisting in combustion ofmany heavier materials, increasing vaporization rates per square foot ofhearth area, effectively obtaining more complete combustion with minimumcarryover of materials to the second oxidation-combustion stage.

All waste material that vaporizes, together with products of combustionof the first stage, fluidizing gases, and excess air, if any, from thefirst forced air supply, pass to the contiguously connected second stageoxidative combustion chamber where a second burner means, and alsofurther forced air supply where required, complete theoxidative-combustion process such that final gaseous products from ourincinerator are fully combusted and essentially smokeless. The quenchingof the hot flue gases exiting from the second stage combustion zone withfresh relatively cool air provides a source of preheated air for eitheror both of the first and second stage combustors, as well as desirablyand suitably providing preheated fluidizing gases to fluidize wastematerials in the first stage to achieve most effective combustion andvaporization.

In general, non-vaporizable matter accumulates in the first stage andcan be removed from the fluidized zone by the traveling grate feature,and removed either periodically or continuously as operating conditionspermit or require. Of course, lighter or thinner combustibles such asliquids or powders can be injected directly into the first stagevaporization zone on a continuous or intermittent basis.

In the embodiment of our fluidized grate two-stage incinerator apparatusand process according to our invention as illustrated by FIG. 1, wastematerials 1 of various types are added 2 into the first stagevaporizaously by various types of feeding devices well known in the art.

In the first stage vaporization zone 3, the waste materials so added areexposed to combustion created by at least one first burner means 4burning any of a variety of fuels 5 such as natural gas, fuel oil,finely divided solid fuels such as powdered coal, or coke, or the like,preferably together with high rate input of preheated forced air 6.

A fluidized bed grate means 7 is shown equipped with traveling gratemeans 8 for continuous or periodic conveyance of non-volatile ash to anash accumulation zone 10. The traveling grate means 8 can be driven byany convenient mechanized means such as a motor-belt drive 9. Underflowpreheated fluidizing gases air are provided 6", 11, to flow upwardly 12through perforated support means 13 to at least partially fluidize wastesolids within combustion zone 3.

In the first stage zone 3, at least one first burner means 4 isillustratively posed with a generally vertically-directed combustionthrust downwardly toward the waste materials positioned, in the case ofsolid and semi-solid material, on or preferably at least partiallyfluidized above grate 7. The first burner means 4 optionally can bepositioned at one angle of thrust in the upper portion of thefirst-stage vaporization zone 3, so

long as the major portion ofthe combustive thrust generally is towardthe waste material to be consumed, vaporized, partially oxidized, or thelike. Preheated forced air supply 6 can enter through or around thefirst burner means 4 as illustrated. Optionally, additional orsupplementary air can be separately blown or otherwise forced into thefirst stage by way of one or more separate access ports or conduit means(not shown).

Products of combusted fuel from the first burner means 4 together withfluidizing gases, excess air, if any, together with vaporized waste, andany products of partial combustion, form a generally gaseous stream 14conducted by confined conduit to enter 16. the contiguous second stagecombustion zone 17 for completion of oxidative combustion.

In the second stage combustion zone 17, fuel 5 is admitted to at leastone second burner means 18, through and/or with which additional andpreferably preheated forced air 6' is admitted to the second stage. Onesecond burner 18 means is illustrated positioned declivously and one 18acclivously toward and thrusting input into the second stage 17. Otherpositions can be used alone or in conjunction, such as horizontal. Thepreheated air supply 6 preferably is over and above that necessary forcombustion of the entering fuel supply 5 to the second burner, andpreferably is in considerable excess of that necessary for combustionpurposes. Such air supply to the second stage 17 can be, if preferred,all or partly fresh air, and optionally can enter the second stage zoneother than via the at least one second burner means 18, 18' asillustrated.

All vaporized, oxidizable components received 14, 16, in the secondstage combustion zone 17 are fully combusted therein, i.e., oxidized asfully as possible, are exited 19, and admixed with quench air 21 priorto exiting to stack means 22, 23. Finally exiting gases 23 areessentially smokeless and indeed have minimal tendency towardatmospheric contamination. If desired, a waste heat boiler or other heatrecovery means may be incorporated 22, if desired.

The second stage combustion zone 17 is equipped at its outlet 19 withquench air inlet means 21, single or multiple, so that the temperatureof the hot gases 19 is sharply reduced by mixing with relatively largequantities of relatively cool ambient air. The temperature reduction canbe controlled within a wide range, depending on relative temperaturesand volumes of the hot gases and the quench air, the temperaturesdesired in the quenched gas stream for heat recovery purposes, or foruse as fluidizing gases, and the like. The quenched gases 22 provide asource of desirably preheated molecular oxygen-containing air 6, 6', 6"for either or both the first 3 or second 17 stage combustion zones orfor the underfire fluidizing air supply 11 in the first stage zone 3 forfluidizing purposes, or for air supply to burner means 4, 18, or anycombination thereof. The recirculated preheated air 6, 6', 6" stillcontains a relatively high molecular oxygen content percentage. Thispreheated air supply 6, 6', 6" not only avoids excessive thermal shockto the system in either stage or to the grate, but being preheated andcontaining molecular oxygen assists in initial combustion in the firststage fluidized bed 7.

The arrangement of our combustion zones need not be as illustrated, butcan incorporate a variety of other relationships. Waste feed input, forexample, can be by means of a hopper means into the first stage zone.While the second stage may be positioned above the first stage asillustrated, the second stage alternatively can be positioned laterallyadjacent to the first stage. Where multiple second stage burners areutilized, one or more may be positioned to thrust more or lesshorizontally, or one or more downwardly and in part upwardly as actuallyillustrated, so long as the combustive thrusts can be generally directedinto the stage wholly or in part tangentially as may be preferred formaximum oxidative combustion. Additional burners can be positioned inthe first stage, if desired, for initial con tacting of the wastematerials entering, or to provide final burn-off of materials from thetraveling grate if desired, or as may be preferred for particularmaterials to be incinerated.

A highly refractory protective lining can be and generally is placedwithin each zone, in the closed conduit means between the zones, and tothe extent necessary in the accumulation zone and stack means. Theemployment of quench air at the exit of the second stage not onlyprovides preheated air for the various purposes as hereinbeforedescribed, but radically cools the exiting gases from the second stageto a degree more compatible for simpler disposal and reduces quitesharply the insulative requirements of the final discharge means 22, 23.

The temperatures reached or maintained in the respective zones willdepend on the materials to be combusted, and can reach elevatedtemperatures in the range of, for example, 200 F. to 2,400 F. or more inthe first stage vaporization zone, and equivalently even higher inrelation thereto in the second stage oxidative combustion zone. Therespective temperatures in the first stage and the second stage can beregulated by the respective degree or extent of firing and respectiveamounts of fuel and air introduced to each burner, and for fluidizingpurposes. More easily volatilized components or materials in the firststage vaporization zone containing the fluidized grate can bevolatilized at lesser temperatures, with primary combustion thencontrolled to occur in the second stage oxidative combustion zone. Moredifficultly volatilizable materials, of

'course, may require higher temperatures in the first wastes, tirecarcasses, other'carcasses where necessary,

more preferred, and the ratio may extend upwardly to as much as about1:6 for additional volume in the second stage and stack when desired, orwhen required by legal restrictions concerning stack sizes and heights.

We suggest as effective and sufficient a relatively small volume secondstage comprared to the first stage of about 3 to l, 2.5 to l to 6:1,preferably. The accumulator zone, where employed, can be of anyconvenient size, .and may be large if desired for convenience insupplying recirculation air. The burners useful in the first and secondstages of our incinerator can be any suitable high combustion rateburners.

Some waste materials, such as paper, carbon, garbage, and the like, canbe completely or virtually completely combusted in the first stage. Suchmaterials ordinarily are slow burning and require auxiliary fuel to Iaccomplish-much in the way of vaporization. An oxidizing atmosphere forsuch materials preferablyis mainoils, and solids.

Reasonable variations and modifications of our invention are possiblewhile still within the scope-of the disclosure, without departing fromthe intended spirit thereof, all as detailed in our specification,drawing, and claims here appended.

We claim:

1. A substantially smokeless two-stage contiguous incinerator forincineration of waste products comprising a .first stage, contiguoussecond stage, connecting means between said first and second stage,exiting gas means from said second stage, quench zone at the outlet ofsaid second stage, and wherein said first stage includes fluidizingmeans positioned generally below said waste products to conductfluidizing gases upwardly through said waste products therebymaintainingsaid waste products in at least a partially fluidized statein said first stage, and conductingmeans for conducting gases from saidquench zone to said fluidizing gas means.

2. The incinerator according to claim 1 further ineluding inlet means insaid quench zone for quench gas tained in the firststage byintroductiontheretoof a higher proportion of excess air than may berequired by other combustibles. With such materials, the fluidizingmeans and fluidized igrate means provide much more uniformly effectiveand quicker. vaporization and partial combustion, while at the same timeproviding more effective utilization of grate area and first zonehorizontal cross sectional area, such that the overall volumetricrequirement of the first zone per volume of waste material to bedisposedof can be greatly reduced from prior incineratormethods andapparatus.

Waste materials such as rubber, water-oil emulsions,"

and the like, may not becompletely burned in the first stage. Suchmaterials are readily vaporizable, however,

and may require little in the'way of auxiliary fuel into the first stageto initiate and maintain vaporization.

- With such readily combusted materials, a reducing atmosphere usuallyperforce results in the first stage, since even with quite high rates ofair input, preheated or otherwise or both, the oxygen consumption canbeso high that a reducing atmosphere may be expected. This is notobjectionable, since the main purpose of the first stage isvaporization.

Conceivably, with some g'asflows from the first zone,

the mere addition of air would provide effective and" satisfactorycomplete oxidative combustion inthesecond stage combustionzone. It willbe apparent that with some waste materials, the fuel requirements in thesecond stage may be low.

Our invention is capable of reducing by incineration the weight andvolume of trash and other waste materials to an exceedingly minorpercentage'as related to the original weight and volume, greatlyreducing the disposal problem. incineration also helps eliminate organicmatter and odors associated therewith. Examples of materials that can becombusted substantially with out production of smoke includepolyethylene pellets and other waste products of polyolefin productionprocesses, various polymeric materials containing ash or catalystcomponents, newspapers, The Wall Street Journal, Pravda, other likeand'unlike garbage, rubber supply, outlet means for conducting gasesfrom said quench zone.

at least one second" burner means in said second zone,

and means for; conducting quench gases from said quench'zone-to .atleast one of said burner meansas air supply thereto. I A I 4. Asubstantially smokeless two-stage contiguous incineratorcomprising:

a. a first stage comprising a vaporization zone, at

least one first burner means, at least one forced air supply means,inlet means for waste materials, outlet meansfor gaseous products, andfluidizing air inlet means, I

b. a second stage comprising a combustion zone, at least one secondburner, at least one second forced I air supply, entrance for receivinggaseous products from said first stage, outlet for combusted. gaseousproducts from said second stage, I I I c. quench air zone and quench.air inlet means,

d; connecting conduit for conducting vaporous products from saidfirst'stage to said second stage by confined means,

e. connecting conduit for conducting vaporous products from said quenchair zone to at least one of saidfirst burner means, second burner means,and fiuidizing'air supply means.

5. The incinerator according to claim 4 wherein at leastone said firstburner is directed from theiupper area of said first stage substantiallydownwardly in said first stage.

6. The incineratoraccording to claim 5 wherein at leastone said firstburner is directed downwardly in a substantially vertical position. I

7. The incinerator according to claim 5 wherein at least one said secondburner means positioned declivously and at least one second burner meansis posi tioned acclivously into said second stage.

8. The incinerator according to claim 5 wherein at least one said secondburner is directed in a substantially horizontal position intosaidsecond stage.

9. The incinerator according to claim wherein the volumetric ratio ofthe first stage to the second stage is from 122.5 to 1:6.

10. The incinerator according to claim 9 wherein the volumetric ratio ofthe first stage to the second stage is about 1:3.

11. The incinerator according to claim 4 wherein each said stage andsaid connecting conduit between said stages is lined with a refractorymaterial.

12. The incinerator according to claim 4 wherein said combusted gaseousproducts from said second stage are passed through a waste heat recoveryunit prior to exhaustion.

13. The incinerator according to claim 4 wherein said waste productsinclude solids, semisolids, and liquids, and are selected from amongstgarbage, rubber wastes, tire carcasses, oils, paper, and plastics.

14. A process of incinerating waste materials comprising the steps of:

a. heating waste materials in the presence of molecular oxygencontaining gases to elevated temperatures while applying preheatedmolecular oxygen containing fiuidizing gases under said waste materials,thereby vaporizing vaporizable components of said waste productssubstantially retaining therein non-vaporizable components of said wasteproducts,

b. separating said vaporized components from said step (a) from saidnon-vaporizable components,

0. oxidatively combusting said vaporized components in the presence ofexcess molecular oxygen containing gases at an elevated temperature, (1.admixing quench air with the vaporous effluent from said step (c),

e. withdrawing at least a portion of the quenched steam from said step(d) as said fluidizing gases in said step (a),

f. exhausting the remaining products of oxidative combustion of saidstep (d) thereby converting said waste products into substantiallynon-vaporizable components and an essentially smokeless oxidizedvaporous effluent.

15. The method according to claim 14 wherein a further portion of saidquenched stream from said step (e) furnishes at least a portion of saidmolecular oxygen stantially in excess of combustive requirements of saidfuel to said steps (a) and (c).

18. The process according to claim 17 wherein the temperature in saidheating-vaporizing step (a) is about 200 to 2,400 F.

19. The process according to claim 18 wherein the temperature in saidoxidative combustion step (c) is substantially higher than saidtemperature in said (a).

20. The incinerator according to claim 3 wherein the volume ratio ofsaid first stage zone to said second stage zone is in the range of 112.5to 1:6.

containing gases in at least one of said steps (a) and

1. A substantially smokeless two-stage contiguous incinerator forincineration of waste products comprising a first stage, contiguoussecond stage, connecting means between said first and second stage,exiting gas means from said second stage, quench zone at the outlet ofsaid second stage, and wherein said first stage includes fluidizingmeans positioned generally below said waste products to conductfluidizing gases upwardly through said waste products therebymaintaining said waste products in at least a partially fluidized statein said first stage, and conducting means for conducting gases from saidquench zone to said fluidizing gas means.
 2. The incinerator accordingto claim 1 further including inlet means in said quench zone for quenchgas supply, outlet means for conducting gases from said quench zone. 3.The incinerator according to claim 2 further including at least onefirst burner means in said first zone, at least one second burner meansin said second zone, and means for conducting quench gases from saidquench zone to at least one of said burner means as air supply thereto.4. A substantially smokeless two-stage contiguous incineratorcomprising: a. a first stage comprising a vaporization zone, at leastone first burner means, at least one forced air supply means, inletmeans for waste materials, outlet means for gaseous products, andfluidizing air inlet means, b. a second stage comprising a combustionzone, at least one second burner, at least one second forced air supply,entrance for receiving gaseous products from said first stage, outletfor combusted gAseous products from said second stage, c. quench airzone and quench air inlet means, d. connecting conduit for conductingvaporous products from said first stage to said second stage by confinedmeans, e. connecting conduit for conducting vaporous products from saidquench air zone to at least one of said first burner means, secondburner means, and fluidizing air supply means.
 5. The incineratoraccording to claim 4 wherein at least one said first burner is directedfrom the upper area of said first stage substantially downwardly in saidfirst stage.
 6. The incinerator according to claim 5 wherein at leastone said first burner is directed downwardly in a substantially verticalposition.
 7. The incinerator according to claim 5 wherein at least onesaid second burner means positioned declivously and at least one secondburner means is positioned acclivously into said second stage.
 8. Theincinerator according to claim 5 wherein at least one said second burneris directed in a substantially horizontal position into said secondstage.
 9. The incinerator according to claim 5 wherein the volumetricratio of the first stage to the second stage is from 1:2.5 to 1:
 6. 10.The incinerator according to claim 9 wherein the volumetric ratio of thefirst stage to the second stage is about 1:3.
 11. The incineratoraccording to claim 4 wherein each said stage and said connecting conduitbetween said stages is lined with a refractory material.
 12. Theincinerator according to claim 4 wherein said combusted gaseous productsfrom said second stage are passed through a waste heat recovery unitprior to exhaustion.
 13. The incinerator according to claim 4 whereinsaid waste products include solids, semisolids, and liquids, and areselected from amongst garbage, rubber wastes, tire carcasses, oils,paper, and plastics.
 14. A process of incinerating waste materialscomprising the steps of: a. heating waste materials in the presence ofmolecular oxygen containing gases to elevated temperatures whileapplying preheated molecular oxygen containing fluidizing gases undersaid waste materials, thereby vaporizing vaporizable components of saidwaste products substantially retaining therein non-vaporizablecomponents of said waste products, b. separating said vaporizedcomponents from said step (a) from said non-vaporizable components, c.oxidatively combusting said vaporized components in the presence ofexcess molecular oxygen containing gases at an elevated temperature, d.admixing quench air with the vaporous effluent from said step (c), e.withdrawing at least a portion of the quenched steam from said step (d)as said fluidizing gases in said step (a), f. exhausting the remainingproducts of oxidative combustion of said step (d) thereby convertingsaid waste products into substantially non-vaporizable components and anessentially smokeless oxidized vaporous effluent.
 15. The methodaccording to claim 14 wherein a further portion of said quenched streamfrom said step (e) furnishes at least a portion of said molecular oxygencontaining gases in at least one of said steps (a) and (c).
 16. Theprocess according to claim 15 wherein said heating-vaporizing step (a)is accomplished by heat produced by the combustion of at least one of afuel and at least a portion of said waste products.
 17. The processaccording to claim 15 wherein at least a portion of said molecularoxygen containing gases is supplied in the form of forced air to atleast one of said steps (a) and (c), and said excess oxygen issubstantially in excess of combustive requirements of said fuel to saidsteps (a) and (c).
 18. The process according to claim 17 wherein thetemperature in said heating-vaporizing step (a) is about 200* to 2,400*F.
 19. The process according to claim 18 wherein the temperature in saidoxidative combustion step (c) is substantially higher than saidtemperature in said (a).
 20. The incinerator according to claim 3wherein the volume ratio of said first stage zone to said second stagezone is in the range of 1:2.5 to 1:6.